1. Technical Field of the Invention
The present invention relates generally to alternators and chagrining systems for automobiles. More particularly, the invention relates to an automotive alternator that has a water shield for protecting brushes of the alternator from water damage.
2. Description of the Related Art
Conventional automotive alternators generally include a rotor mounted on a rotary shaft of the alternator, a stator surrounding the rotor, and a housing that accommodates the rotor and stator.
The rotary shaft has cooling fans fixed thereto, which create cooling air flow with rotation of the shaft. The housing has discharge openings formed therein, through which the cooling air flows out from the housing.
The rotary shaft also has slip rings fixed thereto, which are electrically connected with the rotor and in sliding contact with brushes. The brushes are secured in a brush holder that is fixed to the housing. The slip rings and brushes together form an excitation mechanism by which field current is provided to the rotor while the rotary shaft is rotating.
Additionally, there is provided a rear cover to cover the brush assembly and electrical components, such as a rectifier assembly and a voltage regulator.
In such automotive alternators, it is required to provide a cooling air flow path, through which cooling air can be supplied to the brushes to suppress wear of the brushes due to increase of temperature.
For example, Japanese Utility Model First Publication No. S58-51663 discloses an automotive alternator, in which a groove with the shape of a labyrinth is formed on an end face of a brush holder, so as to provide a cooling air flow path between the brush holder and a seal member.
Japanese Patent Second Publication No. H07-32571, an English equivalent of which is U.S. Pat. No. 4,959,576, discloses an automotive alternator, in which a cooling air flow path is formed within a seal member that is interposed between a brush holder and a rear cover.
Japanese Patent No. 3232706, an English equivalent of which is U.S. Pat. No. 5,424,600, discloses an automotive alternator, in which a groove with the shape of a labyrinth is formed on an end face of a seal member, so as to provide a cooling air flow path between the seal member and a brush holder.
Further, in automotive alternators, it is also required to prevent brushes from water damage. Accordingly, automotive alternators, which have a cooling air flow path formed therein, are required to be so installed in an automobile as to prevent the entrance of the cooling air flow path from being oriented in the direction of a water flow or a water drop in the automobile.
However, recent automotive alternators have become to be installed in automobiles with various orientations. Consequently, in some cases, it is difficult to prevent the entrance of cooling air flow path in an automotive alternator from opening in the direction of water flow or water drop with a standard seal member or brush holder. Accordingly, in such cases, it is necessary to use a special seal member or brush holder depending on the orientation of the automotive alternator in the automobile, thus increasing manufacturing cost of the automotive alternator.